The present invention relates to a chain saw of the type having a plunger piston oil pump having a piston immersed in a chamber filled with oil and rotated by a drive and movable in that chamber to pump oil.
A chain saw of the type under discussion has been disclosed, for example in DE-OS No. 25 41 495 (B27 B, 17/12). In the chain saws of the foregoing type, an end face of the piston immersed in the chamber filled with oil is inclined and this end face is pressed by a spring force against a support element. The support element is adjustable radially to the plunger piston and can serve as an adjusting means to adjust the feeding output of the plunger piston oil pump. Thereby the path of the adjustment is somewhat smaller than the diameter of the piston. Since normally the diameter of the plunger piston can be relatively small the adjustment path is also small and the precision of such adjustment is non-satisfactory. Furthermore, only that end face of the plunger piston which is positioned outside the pump chamber can be always inclined. Therefore the working pressure of the piston acts directly on the support element. All this substantially increases wearing off the support element and the inclined end face of the piston. In the case when the oil being pumped is cold and therefore viscous there is a danger that the pressure on the support element would lncrease so that it can break. In order to avoid such conditions for the immersion piston oil pumps of this type, a releasable flexible drive connection between the piston and the motor driving the same has been additionally required.